Apparatus for making electron-emitting means



May 8, 1928. 1,668,742 E. R. STOEKLE APPARATUS FOR MAKING ELECTRON EMITTING MEANS Filed Jan. 5. 1922 Patented Ma s, 1928.

UNITED STATES PATENT OFFICE.

EB'WIN RUDOLPH STOEKLE, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A. CORPORATION 01 NEW YORK.

APPARATUS FOR MAKING- ELEC'IRON-EMI'ITING MEANS.

Application filed January 5, 1922. Serial No. 527,178.

This invention relates to the manufacture of electron-emitting elements such as electrodes for discharge devices,

The electron emissivity of substances such as platinum is greatly increased when coated with alkaline earth metal oxides, such as barium, strontium and calcium oxide.

It is the object of this invention to provide a simple and efiicient apparatus for and method of applying such a coatng to an electrode element; for example, a lament. This object is accomplished by supporting the filament to be coated and a supply of the coating material within a vessel which is preferably evacuated and heating the coat- 1ng material to ,cause it to be deposited upon thefilament. r

This invention will be better understood by having reference to the following specification and accompanying drawing, wherein the ap aratus is disclosed.

A g ass tube 1 is provided with a neck 2, by means of which it may be attached to a vacuum pump (not shown). In one wall of the tube are sealed the lead wires 3 and 4, to the lower ends of which is attached the filament 5 to be coated. The outer ends of the 7 lead wires 3 and 4 are connected to the terminal of'a battery or other source of electrical energy 6. Sealed in the end of the tube opposite the neck 2 are relatively heavy volatilize by current supplied from a battery 11. The volatilized material is de osited upon the filament 5. After a su cient coating has been deposited, uponwthe .fila-' ment 5, current is passed therethrough means in said chamber oxides. A platinum filament provided with' such a coating has a greater degree of thermionic emissivity than an unco'ated filament operated under thesame temperature conditions.

What is claimed is:

1. In a device of the character described, a chamber, a metallic boat in said chamber 'forholding coating material, means" for heatin said coating material, and means in said 0 iamber for supporting the filament out of contact with the coating material.

2. In a device of the character described; a chamber, a metallic boat in said chamber for holding coating material, lead wires for sup- I porting-said .boat and supplying electrical energy thereto, and means insaid chamberv for supporting a filament out of contact with the coating material.

3. In a device of the character described,

an evacuated chamber, a metallic boat in said chambenfor holdinfg or passing heatin current through said boat to volatilize sai coating material and means for supporting a filament out of contact with the coating material.

4..In a device of the character described, an evacuated chamber, a metallic .boat in said chamber for holding coating material} lead wires for supporting said boat and supplying electrical energy thereto, and means in said chamber for supporting a filameiit out of contact with the coating materla s I In witness whereof, I hereunto subscribe my name this 19th day of December, A'." D. 1921. w

. X, T ERWIN RUDOLPH STOEKLE. i i

coating material, 

